3D Printing Replacement Parts for a Nuclear Warhead

The W80 nuclear warhead is a small American thermonuclear warhead designed for deployment on cruise missiles. A program has been implemented to extend the life of the warhead, called the W80-4 LEP, or life extension program. Recently the National Nuclear Security Administration (NNSA) gave passing grades to the plans to refurbish certain components as well as to the proposed approach to developing component cost estimates.

The warhead, once refurbished, will be paired with a new cruise missile that is being developed by the US Air Force. Lawrence Livermore National Laboratory (LLNL) is the lead nuclear design agency and is working with Sandia National Laboratories, the lead non-nuclear design agency. The work being done on the warhead is to satisfy military requirements to pair the warhead with the new delivery system and improve the weapon’s safety, security and operational logistics, as well as to maintain effectiveness without the need for additional explosive tests. The first production of the W80-4 is scheduled for 2025.

The national laboratories are now focused on making sure that the W80-4 meets requirements. The next step is a detailed weapon development cost report.

Firing Tank Operator Drew Carlson (foreground) safeguards the mouth of the 10kg spherical firing tank at LLNL’s High Explosives Applications Facility as Electronic Technician Raya Yy (background, left) and Ramrod Shawn Strickland wire a high explosive charge for an experiment. The experiment will provide data important to certifying that a refurbished nuclear warhead will work without conducting a full-scale explosive nuclear test.

“Costs are a pretty big deal for us,” said Alicia Williams, LLNL engineering design lead for the LEP. “We go through these detailed reviews of the costs associated with our scope to help management make informed decisions about whether course correction is needed. The net result with this milestone was confirmation that we’re on the right track.”

There are certain challenges associated with refurbishing the warhead. Some aged components and materials cannot be replaced in the same way that they were initially manufactured. The main explosive charge needs replacement, for example, but the original high-explosive constituents are not available and must be reconstituted. Several of the replacement parts are being 3D printed to improve quality and reduce cost – not the first time 3D printing has been used to construct warheads. Researchers at the labs are engineering specific material properties into these replacement parts by controlling the microstructure of the 3D printed material.

To verify that the 3D printed parts will perform as expected, the researchers have already performed a pair of hydrodynamic (full-scale non-nuclear) experiments, back in 2016. The data returned from those tests is being used to ensure that supercomputer simulations accurately represent reality. Thorough material-aging and compatibility experiments are also being undertaken to ensure that the 3D printed material will meet performance requirements for the lifetime of the system.

Those supercomputer simulations and other non-nuclear experiments are crucial to the success of the program. In addition to refurbishing the warhead, the researchers must make sure that it is safe and won’t go off by itself, secure in that it can’t be set off without formal permissions, and effective – all without conducting a full-scale explosive nuclear test. A supercomputer called Sierra is located at LLNL and will play a major role in certifying the replacement warhead. Code advances have also enabled a shift from 2D to 3D modeling, with a special focus on uncertainty quantification, alleviating the reliance on approximations as was required during the nuclear testing era. Hundreds of tests and experiments are currently underway at LLNL and its experimental test site, Site 300.

“This LEP is driving significant innovation at LLNL,” said Des Pilkington, Weapon Physics and Design Program Director. “I’m seeing some really creative work in the options, focused on meeting established performance requirements and to minimize costs, always with an eye to what we can ultimately certify will work. That’s where the experimental and code innovations we’ve made under the Stockpile Stewardship Program come into play. They will be critical to the success of our certification plan.”

Electronic Technician Raya Yy (left) inspects the work of Ramrod Shawn Strickland as he wires a high explosive charge for an experiment.

Five of the 25 major milestones in the LEP are complete so far. Requirements are being refined by the DoD and NNSA, design concepts have been developed, business systems are being put in place to track schedule and budget, and NNSA has invested in the infrastructure at LLNL that will be needed to certify the warhead. In addition, LLNL is leading the effort to reconstitute the capability to manufacture the required insensitive high explosives. Manufacturing of production-scale quantities of the new explosives is proceeding on schedule.

The W80-4 program is scheduled to go into the development engineering phase in 2019. In this phase, researchers will test individual components to ensure that they will meet military requirements. The next phases are production engineering, first production, and full-scale production. To meet the needs of the program, LLNL has taken on significant hiring efforts; more than 100 scientists, engineers and technicians have been hired in 2018 already.

“Even with our Lab hiring at an accelerated rate, and even with the infrastructure improvements NNSA has made here, we could never complete this LEP alone,” said Tom Horrillo, W80-4 LEP Manager. “Our sister lab across the street (Sandia National Laboratories) is playing a central role in this, as are the production plants that are producing components across the country. The Air Force has been a great partner in defining requirements, and NNSA has been indispensable in helping us to roll out the infrastructure and processes we need to get the job done. I’m not overstating things when I say that there would be no LEP without the contributions of everyone on the team.”

The LEP is a collaboration between the DoD and NNSA, with LLNL working with all of the NNSA laboratories and production sites, as well as the Air Force and its missile vendors. Collaborators include Sandia, Kansas City National Security Campus, Y-12 National Security Complex, Pantex Plant, Savannah River Site, Los Alamos National Laboratory, NNSA Livermore Field Office, Albuquerque NNSA W80-4 Program Office, the missile program office at Eglin Air Force Base and Nuclear Weapons Center Kirtland Air Force Base.

“It is so important that we succeed with the W80-4 LEP,” Williams said. “These weapons need to be tremendously safe, secure and effective. We have to meet those expectations just as much as we need to meet the cost and schedule expectations. All told, I can’t help but feel that this is a very exciting time to work at the Lab.”

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